ML20024G962
| ML20024G962 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/28/1975 |
| From: | Stello V Office of Nuclear Reactor Regulation |
| To: | Stuart I GENERAL ELECTRIC CO. |
| Shared Package | |
| ML20024G638 | List: |
| References | |
| NUDOCS 9105030423 | |
| Download: ML20024G962 (5) | |
Text
. _ _ _
n UNIT [D $1 A7f-S N U C!.L Af! HE GULATO. Y C U?.1 JIS5 K.J 4
W ASHifJ G T ON, D.
(.. P O t t t, 2,., 1970 gt, Mr. Ivan F. Stuart, Manager Safety and Licensing t;ucienr Energy Division General Electric Company 175 Curtner Avenue San Joco, California 95114
Dear Mr. Stuart:
/J!TICIPATED TRAtiSIEtiTS WITHOUT SCRAM a y continue our evaluation of yeor cnalysis of in oi d: r t hat t.: -.cins.tec transients uitnout 5cyce,- nttu m ;o, m,
renert.
cdd i < i one. i in.m.ation is required.
ine intonc.. ion required is ocscri! ed in Attachp.nt 1.
Thc responses to tnese concerns cust be provided by Februcry ?G, 1976.
1 Sincerely, 7, /
/!
(t..- f,,.... u
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Victor Stello, Jr., Assistatit Ci: ec tw for Reactor Safety Office of Nuclear Reettcr Regulatior:
Enclosure:
Concccns on NELO 20620 9105030423 750821 PDR ADOCK 05000263 P
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4 CONCERNS ON NEDO 20626 i
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1 Section 7.1 of NEDO 20G26 identifies the systems relied upon toDe I
1.
mitigate tia consequences of ATUS.these systo as and their init further discuss the reliability of these systems to per-Syster form their f un:tions during an ATWS event.
i NEDO 2002f. uses NEDJ 10349 results as bases for concluding 1
Tables 3-1 cnd 3-2 2.
clorure is the most limiting ATWS transient. list thc initial condition
?.nce of LECD 20C..a Provide similar tables used in the NEOS 10349 characteristic.. (Provide the value of the pool temperature in s
i ATWS analysis.
This list should also include the number Table 3-1 of NEDO 20626).
ane! capacitv of each relief / safety valve used in NEDO 10349 and NEDO 2062C analyses.
I. tit cccting on August 7, GE strted that a pool tem-in their analysis (sco rme -
?
!1:ri r.
t r.
'F will te used Navck, USAEC, Septec er 5, 1974).
Nr.00 20E26
.. t frec. A. 1rn.,arn tc T.
Explain the reasons for uses no:>l te terature limit of 170*F.
this change in the temptruture limit and provide an analytical or experirental verificaticn that damaging vibrations in the pool will not occtn below 170"F.
NEDO 20626 does not adequately demonstrate the capability to bring the plant to a cold shutdown and maintain this condition following 4.
j Tnis carability can be demonstrated by meeting the an ATWS.
followin; criteria.
Ability to eeouce vessel pressure a.
i b.
Ability to maintain vessel level Ability to reccove heat in the long term c.
Ji a.
containment pressure ard temperatur c.
Abilit
- 6 within limits Provide thc analyses of the capability to bring the plant to a cold shutdown and maintain this condition for the following three cases.
c.
n:fercn:c cco l
4
. =..
4 l
2 i
1 4
One relief /scfety valve fails to reclose i
b.
for these analyses, provide the following parameters as a function of time until af ter the systems designed for long term cooling (e.g.
RHR or recirculation mode of ECCS) are placed in operation.
1' a.
Reactor power L
b.
Vessel pressure and level 1
HPCI (HPCS) and RCIC flow rato c.
d.
Containment pressure and temperature RHR flow and temperature when RHR is used for suppression pool c.
cooling and decay heat removal Storage capacity of each source of water used to maintain level f.
and remove ener0y from vessel actions including the time action taken n.
Doeratre i
- . 1U ietter fr o I. F. Stuart to V. StcIlo, GF E.
h, t r. 0 toL o to question 4) that the condensate _storace tardi stated (re: pan:es would provice water for HPCI and RCIC for 24 minutes and that tne i
suppression pooi is nct needed as a source of water for an ATt;S event.
1 If. this is the case, explain how the plant can be brought to a cold J.
shutdown condition.
Assuming that the selection and a complete withdrawal of an out-of-sequence rod is a single operator error, provide an analysis of this 6.
Justify the rod worth used in the i
event with s failure to scram.
If GE considers this event not to be an anticipated tran-analysis.
sient, then deranstrate that the reliability of the available pro-The tective equipment is adequate to prevent such an occurrence.
discussion must include the following.
Description of protective equipment used to prevent an occurrence l
a.
of an out-of-sequence rod withdrawal transient the protective eauip-ent cvailable in each plant b.
List Demonstrate that the probability of failure of this equipment is less than 10-# yr. The reliability study must include the time c.
/
the protective equipment may be unavailable.
assume automatic initiation of Ansivses presrnted in NED3 20626 the Sumioy Liquia Controi 5ysten (SLCS) within 7 seconos into the
'/.
Provide an analysis for a loss of normal on-site and transient.
off-site power and demonstrate tnat SLCS will be available when needed to mitigate consequences of this ATWS event, 4
i l
1
j 3
2 Are the results stated in the report NEDO 20626 spolicable to all j
8.
List the set points of the recirculation current class B plants?
pump trip upon high pressure or low water level for each plant.
]
A review of NEDO 10S02 has been complete and our concerns documented, A satisfactory 9.
and in process of being forwarded to General Electric.
response to these concerns must be obtained prior to a complete eval-uation of the current document.
Provide nodal diagrams for fuel modeling, pressure modeling, and mass energy modeling of the BWR 4 plant analyzed.
The significant f eatures 4
of the model used in the analysis are stated.
The validation of the For the stated fe,tures model features is not provided in the report.
- tiso, of the model, provide the reports that validate the features.
l plant analyzed, provide the input data used for the the NT (
for transient code bud the validation for each input parameter.
A specific item on the validation of the model is the void reactivity During an ATWS event resulting in pressurization, it feedback model.
is conservative to assune immediate bubble collapse with pressuri:ation,-
The refor-tous resu)*ing in inrediate positive reactivity feedback.
it rrtir # < ibnie a o void, at nigher surface heat flux levMc 3'
irm rnt m s event, and is thus nonconservative as tN modelt, n cc feedbaci. is negative res;tivity.
Bubble formation and bubble growth are time consuming events and thus it would appear logical to model the recctivity feedback in a manner reflecting the physical phenomenon.
j Provide justification for modeling negative reactivity feedback as an instantaneous result of bubble formation and an estimate of the bubble If this time constant is 0.03 seconds or greater, growth time constant.
provide studies which show the sensitivity of pressure to this time constant.
Wnat is the specific plaat used in NEDO 20626 for which the initici i
10.
conditions are stated? What is the variation in the void reactivity coefficient in each product line?
Section 4.2.2 indicates that " perforation is not precluded." Does 11.
perforation of the cladding due to deformation occur?
If so, provide t
details.
The fuel damari linits used for ATWS by GE adopt those f rom Appendix M.
12.
Although these criteria appear conservative since the LOCA is more severe, the direct applicability of these criteria to ATWS events should be explored for confirmation. The confirmation should consider the effects of previous operation of the fuel, in particular those procersrs which affect cladding stress or strain limits and those i
H irt r 'v trise from fuel - cladding mechanical interaction.
l
--...-e,
,.I-
3 1
4 L
A refined definition of the limits will facilitate post-ATWS event j
decisions relative to subsequent plant operations.
Thus the con-t firmation among the failure (or fuel duty) mechanisms.
13.
Provide any data available on the potential of occurrence for each i
of the transients listed in Section 5.1.
Are there any other tran-j sients that should be included in the list?
14.
The sequence of events for the MSIV Closure Transient states that some fuel experiences transition boiling at four seconds.
Provide J
additional data, i.e., a curve presenting time duration in transition ~
boiling, the percentage of pins in transition boiling, and a discussion j
of this event for the MSIV Closure Transient.
15.
The sensitivity of peak pressure to recirculation pump trip set point is presented in Table 6-1 of NEDO 20626.
For each product line, what is the accuracy of the pressure sensor? What is the variation in time delay?
IG Ti+ sensitivity of peak pressure to relief valve capacity is pivtertti m Table M n UECD 2N26.
For each produ t line, what is tne tir n..-
rei w m cii' For the rinimum relief capacity plants, what is 1:-
relici cn; sci y of eacn valve? What is the probability that a relief valve will not open upon reaching the pressure set point?
Identify B class plants with lower relief capacity than that used in NEDO 200Io.
i Provide ATUS analyses using the plant with the least relief capacility as basis.
i 17.
A more complete description of the Doppler and moderator void coefficients of reactivity used in the ATWS analyses is needed than the values sinply listed in Table 3.1 of NEDO 20626.
Therefore, provide for eech LWR class the following:
a.
The bases and justification for the coefficients used as well as the functional variation of the coefficients throughout the l
j b.
A description of any Doppler and void statistical weighting facturs that may be used.
Values of design conservatism factors (DCF's) that may be used c.
i for each coefficient, d.
Values of the effective delayed neutron fraction and prompt mode neutron generetion time that are used.
18.
Provide in the NEDO LLE2G docuoent, for each BWR class of plants, the i
effect of void and Doppler coefficient variation on the rcsults.
4
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